Reconstruction of a ceramic wafer switch.

[Jamie]

Like the title states.

I have not done this for a long time and the last time I did I only
needed to repair just the wiper fingers. Well, this time I need to
reconstruct most of the wipers on one ceramic wafer and the shorting
plate.

This is for an old SB-1000 Linear Amplifier, It also looks like some
one with very little skills in the field attempted repairs on their own
by looking at the other locations.

The owner of this unit really wants it correct and of course, the
parts are obsolete. It must of been a common problem because I find
hit after hit on the google from those looking for these switches.

So, I have some new ceramic switches here now that I will be drilling
out the rivets for the wipers etc..

This is the problem however, the wiper shorting plate also took a hit
and got burned, warped etc.

What I will be doing is drafting out a new plate on the PC, and
using a thick sheet of brass. I will laser print image at 1:1 and iron
it onto
the plate as a template.

Now because I will be doing this with a rotary tool in a vise and XY
table. I need to glue this plate to a piece of wood or phenolic material
to hold it in place while milling it out.. Of course, I'll need
to where my head magnifiers for this.

When I get done with the edge cutting, I need a way to remove this
plate from the block by softening or some how separating the plate
mildly with out bending it, do any of you know of a way that will soften
the glue? I was thinking of Acetone? But I am not sure about that one?

When done, I will be silver plating this. I also need to get some very
small screws and nuts like around #0-80 for example. I don't feel like
riveting it back together..

So, does my idea of doing this sound plausible if I can find an easy
way to remove the epoxy that will be holding the plate down during the
milling and edging process ?

Jamie

 

[Michael Karas]

[This followup was posted to sci.electronics.design and a copy was sent
to the cited author.]

Perhaps hot glue would suffice ??

My experience is that hot glue can be rather difficult to remove
completely from bare metal like brass or copper.

Many people in the wood working field just use double stick tape to hold
parts together for temporary work. I've even seen it described as being
suitable to hold small parts that were being cut via a router.

You can probably get double stick tape to let go by applying heat with a
heat gun. I've found that to be a very effective means to remove old
shipping labels from cardboard boxes that I want to re-use for shipping
something else.

 

[Jasen Betts]

When I get done with the edge cutting, I need a way to remove this
plate from the block by softening or some how separating the plate
mildly with out bending it, do any of you know of a way that will soften
the glue? I was thinking of Acetone? But I am not sure about that one?

heat it with a blow torch, or hotplate.
that glue will give up before it gets red hot.

Is this piece of such a shape that it can't be cut with snips or a
nibbler?

 

[Jamie]

heat it with a blow torch, or hotplate.
that glue will give up before it gets red hot.

Is this piece of such a shape that it can't be cut with snips or a
nibbler?

No, it has to be routed out, shears would make a mess out of the edges.
These edges must slide under the contact fingers and the plate must stay
conformed.

Jamie

 

[ehsjr]

Like the title states.

I have not done this for a long time and the last time I did I only
needed to repair just the wiper fingers. Well, this time I need to
reconstruct most of the wipers on one ceramic wafer and the shorting
plate.

This is for an old SB-1000 Linear Amplifier, It also looks like some
one with very little skills in the field attempted repairs on their own
by looking at the other locations.

"AL-80 replacement bandswitches fit and they are easier to get"
That's a quote from:
http://lists.contesting.com/_amps/1997-03/msg00269.html

If the quoted sentence is correct, it should save you
a lot of work.

It refers to the Ameritron AL-80 being a clone of the SB-1000.
(vice-versa according to Tom Rauch:
"I designed the AL80A first, and then sold the kit-only rights to Heath.
So the Heath is a "licensed copy" of the AL80A." )

Ed

 

[Jamie]

"AL-80 replacement bandswitches fit and they are easier to get"
That's a quote from:
http://lists.contesting.com/_amps/1997-03/msg00269.html

If the quoted sentence is correct, it should save you
a lot of work.

It refers to the Ameritron AL-80 being a clone of the SB-1000.
(vice-versa according to Tom Rauch:
"I designed the AL80A first, and then sold the kit-only rights to Heath.
So the Heath is a "licensed copy" of the AL80A." )

Ed

Yes, I was made aware of the design being the same however, it seems
that the stock for replacement switches for the AL-80A are also depleted!

I can't seem to find any available out there.

Nice to meet the guy that designed it though.

P.S.

I own myself, a AMERITRON AL-80A and that is still operating fine
with the exception of the zener diode circuit pulled out of there and
replaced it with a circuit and protective fuse. It saves a lot on those
studded odd ball zeners when it decides to arc out if you don't let it
warm up long enough before you hit the PTT line

Jamie